Not Applicable
This invention relates to dippers for large shovels, and particularly to a mechanism for controlling the position of the dipper door that normally closes the bottom of the dipper.
Shovel dippers are formed with teeth at their leading edge and a dipper door that normally closes the rear of the dipper to hold earth and other materials that are loaded into the dipper by the action of the shovel. The dipper door must be held closed while the dipper is being loaded and while the load in the dipper is swung to a deposit point. At that point, the dipper door must be opened to allow the contents of the dipper to fall out. Typically, the locking of the dipper door has been accomplished by a mechanical latch which holds the door in a closed position and which is released by a cable to allow the door to swing open under its own weight and the weight of the contents of the dipper. The door is relatched by allowing it to swing closed. An example of such a mechanical latch is found in U.S. Pat. No. 5,815,958 issued Oct. 6, 1998, for xe2x80x9cExcavator Dipper Latch Assembly Having Removable Tapered Latch Barxe2x80x9d.
The existing mechanical latching mechanisms are subjected to false door release due in part to rocks and dirt being lodged into the latchkeeper mechanism and the wearing away of the structure supporting the dipper door. The existing mechanisms are also subjected to non-release resulting from the mechanical elements failing to disengage properly. The existing mechanisms are further prone to excessive wear and resulting high maintenance costs and efforts.
Uncontrolled motion of the dipper door is currently restrained using snubber mechanisms. An example of such a snubber mechanism is found in U.S. Pat. No. 5,613,308 issued Mar. 25, 1997, for xe2x80x9cDoor Brakexe2x80x9d.
According to the invention, a dynamically active mechanism is used to control the opening of the door. The dynamically active mechanism may also control the door opening speed and may be dynamically active to close the door. It therefore replaces both the mechanical latching and snubber mechanisms currently in use.
The dynamically active mechanism may take the form of a brake or clutch centered at the dipper door hinge point. The dynamically active mechanism may also take the form of a linkage between the dipper and dipper door that is controlled by a linear actuator. A mechanical interlock, such as a spline, key, or sprag, can be engaged and disengaged while the dipper door is static. The dynamically active mechanism is then used to allow the dipper door to move to an open position.
The advantages of a mechanism according to the present invention are that it is capable of holding the dipper door shut under all digging and dumping conditions, it is capable of slowing or stopping the door in any position to allow partial opening or to facilitate xe2x80x9cmetered dumpingxe2x80x9d into a haul truck or other materials transport device, and the exactness of the closed position of the door is not critical since the dipper can be used with the door in any position.
The mechanism according to the present invention maintains the door safely closed during all digging and material transferring operations, allows rapid opening of the dipper door under machine operator""s control, allows metered dumping under machine operator""s control, and retains the ability to have the door close automatically in a safely latched position.